NPC T Type Leg

A block diagram and input parameters for a NPC T Type Leg block is given in Table 1.

Table 1. A NPC T Type Leg block in the Schematic Editor core library

component	component dialog window	component properties
		Property tabs General Timing Model Optimization Losses Weight = 1

The schematic block diagram of the inverter switching block, with corresponding switch arrangement and naming, is given in Figure 1.

Selecting Digital inputs as the Control parameter enables assigning gate drive inputs to any of the digital input pins (from 1 to 32(64)). For example, if S1 is assigned to 1, the digital input pin 1 will be routed to the S1 switch gate drive. In addition, the gate_logic parameter selects either active high (High-level input voltage VIH turns on the switch), or active low (Low-level input voltage VIL turns on the switch) gate drive logic, depending on the external controller design.

Model, when selected for Control parameter, enables the user to set the IGBTs gate drive signals directly from signal processing model. The input pin gates appears on the component and requires a vector input of four gate drive signals in the following order: [S1, S2, S3, S4]. When controlled from the model, logic is always active high.

DTV detection, when enabled DTV detection will be signalized during simulation runtime.

Timing

When Enable delays is enabled, turn on and turn off delay of the IGBTs will be included in the simulation. More information about this feature can be found on the dedicated section switching delay.

PESB Optimization

The PESB Optimization option is available in certain converter models. When PESB Optimization is enabled, all converter's short circuit state space modes will be merged and treated as the same state space mode. For example, if one converter leg within the three phase converter is short circuited and PESB Optimization is enabled, all of the legs within the three phase converter will also be short circuited. This simplification for short circuit modeling can save a significant amount of matrix memory.

Losses calculation

When the Losses calculation property is enabled, the component will calculate switching and conduction power losses for all switching elements (IGBTs and Diodes or MOSFETs). In the case of MOSFET switching elements, the diode characteristic represents the internal MOSFET body diode. Switching power losses are calculated as a function of current, voltage, and temperature using 3D lookup tables. Also, 2D input for losses is supported. When a 2D losses table is inserted, it assumes only current (I) and temperature dependence. From version 2020.3, conduction power losses can be defined as a function of current and temperature using Vt and Vd lookup tables (LUTs) (the previous option of using Vce, Rce, Vd, and Rd properties are removed). These LUTs can be 1D or 2D tables. If the LUT is a 1D table, forward voltage drop depends only on current, but if LUT is a 2D table, forward voltage drop dependence on the junction temperature is also considered. In the MOSFET case under reverse current conduction, a current sharing calculation between the MOSFET channel and the internal body diode is performed. Import options and an explanation how to correctly fill all necessary power losses parameters is described in the import power losses section. All switches are distributed in two groups, and for each group, different power loss parameters can be specified (S1 and S4 are in group 1, S2 and S3 are in group 2).

If the IGBT switch types are used in both losses groups, input/output terminals for power losses are vectors of eight elements (every index in the vector represent one switching element). Ordering of switching elements is given in the next table.

If the MOSFET switch types are used in both losses groups, input/output terminals for power losses are vectors of four elements (every index in the vector represent one switching element). Ordering of switching elements is given in the next table.

If the MOSFET switch type is used for losses group 1 and IGBT switch type for losses group 2, input/output terminals for power losses are vectors of six elements (every index in the vector represent one switching element). Ordering of switching elements is given in the next table.

• Losses groups - Switching elements group

• Current values - Switching elements current axis [A]

• Voltage values - Switching elements voltage axis [V]

• Temp values - Switching elements temperature axis [°C]

• Vce - IGBT collector emitter saturation voltage [V] - discontinued from 2020.3 release

• Rce - IGBT on state slope resistance [Ohm] - discontinued from 2020.3 release

• Vd - IGBT Diode voltage drop [V] - discontinued from 2020.3 release

• Rd - IGBT Diode slope resistance [Ohm] - discontinued from 2020.3 release

• Vt table - Switch forward voltage drop, f(I,T) [V]

• Vd table - Diode forward voltage drop, f(I,T) [V]

• Et on table - Switch switching ON losses, output energy, f(I, V, T) [J]

• Et off table - Switch switching OFF losses, output energy, f(I, V, T) [J]

• Ed off table - Diode switching OFF losses, output energy, f(I, V, T) [J]

  Note: Automatic initialization of the Vt table and Vd table properties will be performed based on the discontinued Voltage and Resistance properties (Vce, Rce, Vd, Rd).

Temperatures calculation

Vienna rectifier optimization

Vienna rectifier optimization is activated through the corresponding checkbox in the Model Optimization tab. S1 and S4 IGBTs are removed from the circuit, leaving only the diodes. This results in a single leg of a three-phase topology commonly known as Vienna rectifier. This reduces time slot utilization and can enable the model to run at a shorter simulation time step.

Digital Alias

If a converter is controlled by digital inputs, an alias for every digital input used by the converter will be created. Digital input aliases will be available under the Digital inputs list alongside existing Digital input signals. The alias will be shown as Converter_name.Switch_name, where Converter_name is name of the converter component and Switch_name is name of the controllable switch in the converter.